As the integrated circuit technology advances towards ever increasing large-scale integration and high performance circuits, it is necessary to provide interconnection electrical packaging that is compatible with the performance demands of the associated device technology. Thus the problems of signal delay, package impedence and cross talk are extremely critical. The principles of transmission line technology must be engineered into the semiconductor packages in order to handle the extremely high device switching speeds.
Laminated multi-layer boards provided with internal wiring are well known as illustrated and described in U.S. Pat. No. 3,564,114. Multi-layer ceramic substrates capable of mounting and interconnecting a plurality of semiconductor devices are also well known as indicated by an article entitled "A Fabrication Technique for Multi-Layer Ceramic Modules" by H. D. Kaiser et al. in Solid State Technology, May 1972 P. 35-40. In this technology green sheets of ceramic, i.e., ceramic powder held together in sheet form by temporary organic binders, are metalized with noble or refractory metals, usually by screen printing. The metalized sheets are stacked, laminated, and fired to form a monolithic ceramic package. This technology affords an opportunity to do three-dimensional wiring in what was formerly waste or inaccessible space in a ceramic substrate. The use of this waste space results in the creation of the high density, sturdy electronic package with good performance and reliability. With the advent of microminiaturized large scale integrated circuit semiconductor devices with their accompanying faster speeds of operation, the compatibility of the substrate and the devices supported thereon became extremely important. In order to control and predict the operating characteristics of the substrate, such as signal delay, cross talk, etc., it becomes increasingly important to control the impedance and capacitance characteristics of the internal wiring, as well as the length. The increased density of the semiconductor devices on the substrate also imposes formidable cooling requirements in order to maintain the temperature of the device as safe operating ranges during operation.